1. Field of the Invention
The present invention relates to an illuminating device that emits a plurality of beams of which colors are different from one another, a projecting device, and a method for controlling a projecting device.
2. Description of the Related Art
Conventionally, information can be shared with attendants in a conference or the like by projecting screen information of an information processor such as a personal computer (PC) onto a screen using a projector.
In such a projector, a high-luminance discharge lamp such as an extra high pressure mercury lamp is used as a light source predominately in a conventional technique. The discharge lamp can realize high luminance at low cost. However, an alternative light source is desired because the discharge lamp takes time to provide a predetermined amount of light emission from the start of lighting and involves some environmental concerns.
To address this issue, solid light emitting elements such as light emitting diodes (LED) of red (R), green (G), and blue (B) and organic electroluminescence (EL) devices have been developed to be used as a light source that is an alternative to the discharge lamp in a projector and have been put into practical use. The projector can be activated at high speed and environmental concerns can be eliminated by using these solid light emitting elements as the light source of the projector.
A technique of obtaining light components of various colors using a blue laser or a light emitting diode that emits light of blue, as one of the solid light emitting elements, has been put into practical use. For example, when the blue laser is used, if laser light output from the blue laser is emitted onto a phosphor, the phosphor is excited and light of a color unique to the phosphor is emitted. By using this characteristic, light components of colors of R, G, and B can be obtained. Furthermore, a technique of using the light obtained by the phosphor as a light source of a projector has been developed. Gradations of the light components of the colors of R, G, and B obtained as described above are controlled by using a spatial light modulating element such as a digital micromirror device (DMD) for each pixel so as to obtain a color projected image.
It is to be noted that when a blue laser is used as a light source of a projector, for example, if one laser diode is used for one color, a light amount is insufficient. Therefore, in general, a laser diode array in which several to several dozens of laser diodes are configured integrally is used as a light source.
Japanese Patent Application Laid-open No. 2004-341105 discloses a projection-type display device having a light emitting diode, a phosphor layer that converts ultraviolet light emitted by the light emitting diode to visible light, and a transparent base material.
According to Japanese Patent Application Laid-open No. 2004-341105, a disk is divided into three regions. Furthermore, a visible light reflecting film through which ultraviolet light is transmitted and that reflects visible light is formed on each region at an incident side and a phosphor layer that converts a wavelength of the ultraviolet light into a wavelength of each color of R, G, and B is formed on each region at an emitting side opposed to the incident side with a transparent layer interposed therebetween. If the disk is rotated, the ultraviolet light from a light source is converted into light components having wavelengths of R, G, and B by the phosphor layers in the regions. Then, repetitious color light components of R, G, and B are emitted. The color light components are emitted on a spatial light modulator, so that optical modulation is performed on the light components. Then, the modulated light is projected onto a screen through a projection lens in an enlarged manner.
Japanese Patent Application Laid-open No. 2009-277516 discloses a light source device and a projector in which phosphor layers are arranged in a plurality of segment regions of a circular transparent base material, and visible light of which energy is lower than ultraviolet light is emitted onto phosphors as exciting light so as to obtain light components of colors.
In the conventional techniques as disclosed in Japanese Patent Application Laid-open No. 2004-341105 and Japanese Patent Application Laid-open No. 2009-277516, the disk is radially divided into a plurality of regions, phosphor layers that emit different colors are formed in the divided regions, and the disk is rotated, so that light components of the colors are emitted in a time-division manner. Therefore, laser light is emitted onto a limited area in a concentrated manner on the phosphor layer of each color, so that the irradiated portion is made into a so-called “burned” state. This may deteriorate the characteristic of the phosphor layers.
In order to prevent deterioration of the characteristic of the phosphor layers due to irradiation of the laser light on a specific portion of each color in a concentrated manner, it is considered that the disk is not divided into regions of the colors and a disk including a phosphor layer for each color is provided. This requires disks corresponding to the number of colors in one device, resulting in increased cost and device size.
There is need to reduce the size of a device in which a phosphor is excited to obtain light of each color at lower cost.